Calorimetric study of the copolymers on basis perfluorinated germanium hydrides with different structures

The temperature dependences of heat capacity of copolymers on the basis of perfluorinated germanium hydrides have been measured using an adiabatic vacuum calorimeter over the temperature range from 6 K to the final temperature of their stability for the first time. Thus, the physical transformations were detected and their thermodynamic characteristics were estimated. The experimental results were used to calculate the standard thermodynamic functions, namely heat capacity, enthalpy, entropy and Gibbs function over the range from T → 0 to the final temperature stability of copolymers. The standard entropy of formation of the under study copolymers at T = 298.15 K was calculated. The obtained results were compared with corresponding data for hyperbranching perfluor polyphenylenegermaniums with other structures. Some conclusions about dependences of the thermodynamic polymers properties versus their structures were made.     

Synthesis and properties of hyperbranched copolymers based on perfluorinated germanium hydrides

Hyperbranched copolymers of various structures and molecular masses in the range 2.0 × 10⁴?4.4 × 10⁵ are prepared via the activated copolycondensation of tris- and bis(pentafluorophenyl)germane in tetrahydrofuran performed in the presence of triethylamine as an activator. The kinetics of copolycondensation is studied via the method of heat-conduction reaction calorimetry. It is found that tris(pentafluorophenyl)germane shows a higher activity in copolycondensation than bis(pentafluorophenyl)germane. Shear moduli, loss factors, and glass-transition temperatures of the copolymers are determined by dynamic mechanical analysis and differential-scanning calorimetry. The copolymers feature glass-transition temperatures up to 250°C. These values are considerably higher than those of perfluorinated polyphenylenegermane (162°C).     

Synthesis and self-organization of amphiphilic poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone-2,2,3,3-tetrafluoropropyl methacrylate) diblock copolymers in solution and bulk

It is shown that the amphiphilic diblock copolymers poly(N-vinylpyrrolidone-2,2,3,3-tetrafluoropropyl methacrylate) can be prepared through the reaction of chain transfer to bis(pentafluorophenyl)germane during the polymerization of N-vinylpyrrolidone and the subsequent postpolymerization of isolated functional polymers in 2,2,3,3-tetrafluoropropyl methacrylate. The dilute-solution behavior and self-organizing ability of functional polymers based on poly(N-vinylpyrrolidone) containing end bis(pentafluorophenyl) groups and of amphiphilic diblock copolymers formed on their basis are studied via the methods of static and dynamic light scattering and viscometry. Surface properties at the interface of the films are estimated through the wetting technique.     

Thermodynamics of cross-linked and branched (co)polymers based on <Emphasis Type="Italic">tris</Emphasis>- and <Emphasis Type="Italic">bis</Emphasis>-(pentafluorophenyl)germanes

The temperature dependence of the heat capacity of cross-linked and branched (co)polymers based on tris- and bis-(pentafluorophenyl)germanes is studied in the temperature range of 6–7 to 535–570 K, using adiabatic vacuum and differential scanning calorimeters. In the indicated temperature range, physical transformations are revealed and their thermodynamic characteristics are determined. The obtained experimental data are used to calculate the thermodynamic functions of (co)polymers: C _p /°, H°(T) - H°(0), S°(T) - S°(0), and G°(T) - H°(0) in the range of T → 0 to 535 K for the branched (co)polymer and from T → 0 to 500 K for the cross-linked polymer. Their standard entropies of formation are determined at 298.15 K. The obtained results are compared with analogous data for hyperbranched perfluorinated polyphenylenegermane studied earlier. The effect of the structure of polyphenylenegermanes on their thermodynamic properties is analyzed.     

Controlled Synthesis of Methacrylic Acid-Methyl Acrylate Copolymers and Their Properties at Various Interfaces

Russian Journal of Applied Chemistry - Conditions were found for controlled reversible addition-fragmentation chain-transfer radical polymerization to obtain narrow-dispersity gradient methacrylic...     

Properties of Methacrylic Acid–Methyl Acrylate Copolymers of Varied Structure

Physicomechanical and surface properties of films of copolymers of methacrylic acid with methyl acrylate, which have close compositions and molecular masses (M_n ≈ 5.7 × 10⁴) and various chain structures (gradient copolymer and statistical copolymer), were studied. The thermodynamic characteristics of the copolymers were determined; two glass-transition points (29.6 and 141.0°C) were found for the gradient copolymer, and one glass-transition point of 40.1°C, for the copolymer with a statistical distribution of units along the chain. It was found that more mechanically strong films with tensile stress of 2.8 MPa are characteristic of the gradient copolymer. The wetting method was used to determine by using the Hood–Kaelble–Dann–Fowkes approach the surface Gibbs energies of the films and their polar and dispersion components. Atomic-force microscopy was used to find heterogeneities (0.1–0.3 μm) on the surface of a film of a statistical copolymer, whereas the film of a gradient polymer has a homogeneous structure.     

Linear-Dendritic Block Copolymers Based on <Emphasis Type="Italic">N</Emphasis>-Isopropylacrylamide and Perfluorinated Polyphenylenegermane: Synthesis and Properties at Various Interfacial Boundaries

It is shown that linear-dendritic block copolymers poly(N-isopropylacrylamide)–block–polyphenylenegermane can be prepared by the polymerization of N-isopropylacrylamide in the presence of bis(pentafluorophenyl)germane followed by activated polycondensation with tris(pentafluorophenyl)germane. The properties of the dilute solutions and Langmuir monolayers of the functional polymers and the linear-dendritic block copolymers of N-isopropylacrylamide are studied.     

Conformation of the Linear-Dendritic Block Copolymers of Hyperbranched Polyphenylenegermane and Linear Poly(methylmethacrylate)

Dilute solutions of linear-dendritic block copolymers of linear poly(methylmethacrylate) with hyperbranched polyphenylenegermane were investigated by light scattering methods. The obtained results were compared with characteristics of functionalized poly(methylmethacrylate) with -Ge(C₆F₅)₃ terminal groups, linear poly(methylmethacrylate), and hyperbranched polyphenylenegermane. The investigated samples differ by molar masses of the linear components. It was shown that molecules of functionalized poly(methylmethacrylate) in solution have a conformation that is typical for linear polymers in good solvent, while the linear-dendritic polymers in dilute chloroform solution have compact structure and high density in comparison with linear poly(methylmethacrylate).     

Calorimetric and structural studies of organic compound of tris(pentafluorophenyl)-4-pyridylethylgermane

In the present research, the temperature dependence of heat capacity of tris(pentafluorophenyl)-4-pyridylethylgermane (C₆F₅)₃Ge–CH₂–CH₂–C₅H₄N was studied by precise adiabatic vacuum calorimetry and differential scanning calorimetry over the temperature range from 6 to 450 K. The temperature and enthalpy of fusion of tris(pentafluorophenyl)-4-pyridylethylgermane and the total mole fraction of impurities have been determined. The thermal stability of the sample was investigated by thermogravimetric analysis. The experimental data were used to calculate the standard thermodynamic functions: heat capacity, enthalpy, entropy, and the Gibbs energy over the range from T → 0 to 420 K for crystalline and liquid states. For the compound under study, the standard entropy of formation in the crystalline state was calculated at T = 298.15 K. In addition, the structure of the investigated compound was established, and corresponding structural parameters were determined.